Ipsilateral and contralateral subthalamic activity after unilateral dopaminergic lesion.

Unilateral lesions of the dopaminergic nigral neurons in rats are currently used as a model of Parkinson's disease. However, several neurochemical studies have questioned the possible influence of the lesioned side on the contralateral non-lesioned side. To address this question, electrophysiological recordings in the ipsilateral and contralateral subthalamic nucleus was performed on anaesthetized rats, 3, 7 and 14 days after induction of a unilateral dopaminergic lesion. At these three times, the mean discharge rate of the subthalamic neurons recorded ipsilateral to the lesion was increased by 85, 176 and 127%, respectively, whereas this rate was decreased by 16, 27 and 43%, respectively, in the opposite subthalamic nucleus. This result emphasizes the importance of interhemispheric regulation of this structure, contrasting with the unilateralized current model of the functional organization of the basal ganglia.